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8178355: IdentityHashMap uses identity-based comparison for values ev…
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…erywhere except remove(K,V) and replace(K,V,V)

Reviewed-by: smarks
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stuart-marks authored and Stuart Marks committed Nov 3, 2022
1 parent 25dfcbd commit 53905e6
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Showing 2 changed files with 164 additions and 13 deletions.
82 changes: 72 additions & 10 deletions src/java.base/share/classes/java/util/IdentityHashMap.java
Expand Up @@ -49,6 +49,10 @@
* designed for use only in the rare cases wherein reference-equality
* semantics are required.</b>
*
* <p>The view collections of this map also have reference-equality semantics
* for their elements. See the {@link keySet() keySet}, {@link values() values},
* and {@link entrySet() entrySet} methods for further information.
*
* <p>A typical use of this class is <i>topology-preserving object graph
* transformations</i>, such as serialization or deep-copying. To perform such
* a transformation, a program must maintain a "node table" that keeps track
Expand Down Expand Up @@ -346,7 +350,8 @@ public V get(Object key) {

/**
* Tests whether the specified object reference is a key in this identity
* hash map.
* hash map. Returns {@code true} if and only if this map contains a mapping
* with key {@code k} such that {@code (key == k)}.
*
* @param key possible key
* @return {@code true} if the specified object reference is a key
Expand All @@ -370,7 +375,8 @@ public boolean containsKey(Object key) {

/**
* Tests whether the specified object reference is a value in this identity
* hash map.
* hash map. Returns {@code true} if and only if this map contains a mapping
* with value {@code v} such that {@code (value == v)}.
*
* @param value value whose presence in this map is to be tested
* @return {@code true} if this map maps one or more keys to the
Expand Down Expand Up @@ -411,8 +417,9 @@ private boolean containsMapping(Object key, Object value) {

/**
* Associates the specified value with the specified key in this identity
* hash map. If the map previously contained a mapping for the key, the
* old value is replaced.
* hash map. If this map already {@link containsKey(Object) contains}
* a mapping for the key, the old value is replaced, otherwise, a new mapping
* is inserted into this map.
*
* @param key the key with which the specified value is to be associated
* @param value the value to be associated with the specified key
Expand Down Expand Up @@ -497,8 +504,10 @@ private boolean resize(int newCapacity) {

/**
* Copies all of the mappings from the specified map to this map.
* These mappings will replace any mappings that this map had for
* any of the keys currently in the specified map.
* For each mapping in the specified map, if this map already
* {@link containsKey(Object) contains} a mapping for the key,
* its value is replaced with the value from the specified map;
* otherwise, a new mapping is inserted into this map.
*
* @param m mappings to be stored in this map
* @throws NullPointerException if the specified map is null
Expand All @@ -516,6 +525,8 @@ public void putAll(Map<? extends K, ? extends V> m) {

/**
* Removes the mapping for this key from this map if present.
* The mapping is removed if and only if the mapping has a key
* {@code k} such that (key == k).
*
* @param key key whose mapping is to be removed from the map
* @return the previous value associated with {@code key}, or
Expand Down Expand Up @@ -632,7 +643,9 @@ public void clear() {
* {@code true} if the given object is also a map and the two maps
* represent identical object-reference mappings. More formally, this
* map is equal to another map {@code m} if and only if
* {@code this.entrySet().equals(m.entrySet())}.
* {@code this.entrySet().equals(m.entrySet())}. See the
* {@link entrySet() entrySet} method for the specification of equality
* of this map's entries.
*
* <p><b>Owing to the reference-equality-based semantics of this map it is
* possible that the symmetry and transitivity requirements of the
Expand Down Expand Up @@ -667,8 +680,11 @@ public boolean equals(Object o) {

/**
* Returns the hash code value for this map. The hash code of a map is
* defined to be the sum of the hash codes of each entry in the map's
* {@code entrySet()} view. This ensures that {@code m1.equals(m2)}
* defined to be the sum of the hash codes of each entry of this map.
* See the {@link entrySet() entrySet} method for a specification of the
* hash code of this map's entries.
*
* <p>This specification ensures that {@code m1.equals(m2)}
* implies that {@code m1.hashCode()==m2.hashCode()} for any two
* {@code IdentityHashMap} instances {@code m1} and {@code m2}, as
* required by the general contract of {@link Object#hashCode}.
Expand Down Expand Up @@ -1162,7 +1178,9 @@ public Spliterator<V> spliterator() {
* e.getValue()==o.getValue()}. To accommodate these equals
* semantics, the {@code hashCode} method returns
* {@code System.identityHashCode(e.getKey()) ^
* System.identityHashCode(e.getValue())}.
* System.identityHashCode(e.getValue())}. (While the keys and values
* are compared using reference equality, the {@code Map.Entry}
* objects themselves are not.)
*
* <p><b>Owing to the reference-equality-based semantics of the
* {@code Map.Entry} instances in the set returned by this method,
Expand Down Expand Up @@ -1382,6 +1400,50 @@ public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
}
}

/**
* {@inheritDoc}
*
* <p>More formally, if this map contains a mapping from a key
* {@code k} to a value {@code v} such that {@code (key == k)}
* and {@code (value == v)}, then this method removes the mapping
* for this key and returns {@code true}; otherwise it returns
* {@code false}.
*/
@Override
public boolean remove(Object key, Object value) {
return removeMapping(key, value);
}

/**
* {@inheritDoc}
*
* <p>More formally, if this map contains a mapping from a key
* {@code k} to a value {@code v} such that {@code (key == k)}
* and {@code (oldValue == v)}, then this method associates
* {@code k} with {@code newValue} and returns {@code true};
* otherwise it returns {@code false}.
*/
@Override
public boolean replace(K key, V oldValue, V newValue) {
Object k = maskNull(key);
Object[] tab = table;
int len = tab.length;
int i = hash(k, len);

while (true) {
Object item = tab[i];
if (item == k) {
if (tab[i + 1] != oldValue)
return false;
tab[i + 1] = newValue;
return true;
}
if (item == null)
return false;
i = nextKeyIndex(i, len);
}
}

/**
* Similar form as array-based Spliterators, but skips blank elements,
* and guestimates size as decreasing by half per split.
Expand Down
95 changes: 92 additions & 3 deletions test/jdk/java/util/IdentityHashMap/Basic.java
Expand Up @@ -38,7 +38,7 @@

/*
* @test
* @bug 8285295
* @bug 8285295 8178355
* @summary Basic tests for IdentityHashMap
* @run testng Basic
*/
Expand All @@ -49,8 +49,6 @@
// the identities of Map.Entry instances obtained from the entrySet; however, the keys and
// values they contain are guaranteed to have the right identity.

// TODO remove(k, v)
// TODO replace(k, v1, v2)
// TODO add tests using null keys and values
// TODO deeper testing of view collections including iterators, equals, contains, etc.
// TODO Map.Entry::setValue
Expand Down Expand Up @@ -484,6 +482,97 @@ public void testRemoveKey() {
entry(k2, v2));
}

// remove(Object, Object) absent key, absent value
@Test
public void testRemoveAA() {
Box k1c = new Box(k1a);
Box v1c = new Box(v1a);
assertFalse(map.remove(k1c, v1c));
checkEntries(map.entrySet(),
entry(k1a, v1a),
entry(k1b, v1b),
entry(k2, v2));
}

// remove(Object, Object) absent key, present value
@Test
public void testRemoveAV() {
Box k1c = new Box(k1a);
assertFalse(map.remove(k1c, v1a));
checkEntries(map.entrySet(),
entry(k1a, v1a),
entry(k1b, v1b),
entry(k2, v2));
}

// remove(Object, Object) present key, absent value
@Test
public void testRemoveKA() {
Box v1c = new Box(v1a);
assertFalse(map.remove(k1a, v1c));
checkEntries(map.entrySet(),
entry(k1a, v1a),
entry(k1b, v1b),
entry(k2, v2));
}

// remove(Object, Object) present key, present value
@Test
public void testRemoveKV() {
assertTrue(map.remove(k1a, v1a));
checkEntries(map.entrySet(),
entry(k1b, v1b),
entry(k2, v2));
}

// replace(K, V, V) absent key, absent oldValue
@Test
public void testReplaceAA() {
Box k1c = new Box(k1a);
Box v1c = new Box(v1a);
Box newVal = new Box(v2);
assertFalse(map.replace(k1c, v1c, newVal));
checkEntries(map.entrySet(),
entry(k1a, v1a),
entry(k1b, v1b),
entry(k2, v2));
}

// replace(K, V, V) absent key, present oldValue
@Test
public void testReplaceAV() {
Box k1c = new Box(k1a);
Box newVal = new Box(v2);
assertFalse(map.replace(k1c, v1a, newVal));
checkEntries(map.entrySet(),
entry(k1a, v1a),
entry(k1b, v1b),
entry(k2, v2));
}

// replace(K, V, V) present key, absent oldValue
@Test
public void testReplaceKA() {
Box v1c = new Box(v1a);
Box newVal = new Box(v2);
assertFalse(map.replace(k1a, v1c, newVal));
checkEntries(map.entrySet(),
entry(k1a, v1a),
entry(k1b, v1b),
entry(k2, v2));
}

// replace(K, V, V) present key, present oldValue
@Test
public void testReplaceKV() {
Box newVal = new Box(v2);
assertTrue(map.replace(k1a, v1a, newVal));
checkEntries(map.entrySet(),
entry(k1a, newVal),
entry(k1b, v1b),
entry(k2, v2));
}

// AN: key absent, remappingFunction returns null
@Test
public void testComputeAN() {
Expand Down

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